A conventional positioner is constructed as shown in FIG. 5 (see, e.g., Patent Document 1).
In the figure, 512 designates an electrically conductive rotating table which fixes and rotates a welding object or a jig 501. 502 designates an electrically conductive hollow shaft which is press-fitted and fixed to the center of the rotating table 512. 503 designates an electrically conductive ring of a donut disk shape which is fixed to the other end of the hollow shaft 502. 504 designates a carbon brush which comes in contact with the ring 503 from below. 505 designates a cable connected to the carbon brush 504. The cable 505 is for sending a welding electric current to an external welding electric power source. 506 designates a first pulley fixed to the hollow shaft 502. 507 designates a second pulley connected to a motor 508. 509 designates a timing belt which links the first pulley 506 and the second pulley 507. 510 designates an external mounting case. 511 designates an air tube or a cable.
In the conventional positioner, the hollow shaft 502 is driven by the motor 508 via the timing belt 509 and the pulleys 506, 507, thereby rotating the rotating table 512. In such a configuration, the air tube or the cable 511, which supplies air or electric power used in driving the jig 501 on the table, is set on the rotating table 512 by being led through the interior of the hollow shaft 502 from a bottom portion of a positioner. The welding electric current flows from the rotating table 512 to the exterior through the carbon brush 504.    Patent Document 1: Japanese patent No. 3019068